In recent years, the computer industry has strived to introduce printed circuit board (PCB) substrates having low attenuation at high frequencies, for example at frequencies greater than 1 GHz. Relatedly, the industry has further endeavored to lower attenuation in PCB substrates that may employ odd mode propagation via differentially coupled traces. These attenuation loses are associated with the loss tangent of the PCB substrate composite material, wherein the complex dielectric constant, ∈r, of the composite material varies by frequency and may be expressed by the following equation:∈r=∈′r−j∈″r, wherein                ∈′r is the relative permittivity of the composite material which varies as a function of frequency; and        ∈″r is the loss factor of the composite material which varies as a function of frequency.Loss tangent, tan δ, may be defined by the following equation in terms of the relative permittivity, ∈′r, and the loss factor, ∈″r:tan δ=∈″r/∈′r         
Existing PCB substrates include signal traces disposed in a composite dielectric material, such as a Fire Retardant (FR)-4 material, which is an inexpensive composite material formed by glass strands embedded in an epoxy resin. During the curing of the dielectric material, the resin component and the glass component cure at different rates, thereby creating a phase separation defined by a glass phase that is superposed over a resin phase. Generally, the resin phase has a higher loss tangent than the glass phase and in particular instances the resin phase may have a loss tangent as high as 0.4. Hence, the high loss resin settling between the signal traces can cause a significant amount of differential mode signal attenuation. Presently, the differential mode attenuation in PCB substrates is lowered by constructing the entire PCB substrate from materials having low loss tangents. Low loss tangent materials, however, add significant material costs to PCB substrate construction.